Reversible sorafenib-associated coagulopathy identified by viscoelastic testing in a dog with intranasal sarcoma

Sorafenib is a multi-kinase inhibitor increasingly used in veterinary oncology, but information regarding its potential adverse hematologic effects in dogs remains limited. A 50 kg neutered male Labrador Retriever with previously treated intranasal sarcoma was treated with sorafenib (5 mg/kg PO q24h) based on tyrosine kinase receptor profiling that identified 60% overexpression of platelet-derived growth factor receptor. The dog remained clinically stable for 132 days before developing worsening nasal discharge, increased epistaxis, and respiratory effort. Hematologic testing identified a platelet count of 130 × 103/μL with clumping, normal prothrombin time, activated partial thromboplastin time, and normal D-dimer concentration. Computed tomography did not indicate appreciable tumor progression. Viscoelastic assessment demonstrated delayed clot initiation and markedly decreased clot development and firmness, consistent with a hypocoagulable profile. Sorafenib was discontinued, and serial viscoelastic testing on days 149, 170, and 191 showed progressive improvement with normalization of clot parameters, paralleling the resolution of clinical signs. This case documents reversible, sorafenib-associated coagulopathy in a dog and illustrates the diagnostic utility of viscoelastic testing when evaluating worsening epistaxis in dogs receiving tyrosine kinase inhibitors.